Oil return control method, device and multi-connection system

Abstract

The present invention provides an oil return control method, device, and multi-split system; wherein, the method includes: obtaining the outlet temperature of the oil return capillary in real time; judging whether there is refrigerant in the oil return capillary based on the outlet temperature and a preset temperature threshold; if so, performing current oil return control on the multi-split system; in the current oil return control, calculating the flow rate of the refrigerant based on calculation parameters and a preset flooding formula; calculating the corresponding oil return frequency of the compressor in the current oil return control based on the displacement and volume coefficient of the compressor, as well as the flow rate and the inner diameter of the piping; and controlling the compressor to operate according to the oil return frequency. In the above-mentioned oil return control method, whether there is refrigerant in the oil return capillary is intelligently judged based on the outlet temperature. When refrigerant is present, current oil return control is performed, and in the oil return control, the corresponding oil return frequency of the compressor is calculated based on the calculation parameters and the preset flooding formula, thereby ensuring oil return reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular to an oil return control method, device and a multi-connected system. Background Art

[0002] Oil return control is a key technology for multi-split heat pump air conditioners, crucial for compressor reliability. During the oil return process, increasing the compressor frequency and controlling the opening of the electronic expansion valve during shutdown can cause noise and other issues, impacting air conditioning comfort. Existing oil return control primarily uses the air conditioner's operating time as a criterion for whether to initiate oil return. This system also employs a fixed oil return frequency, leading to frequent compressor oil return and reduced oil return efficiency. Therefore, ensuring effective oil return is a pressing issue. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an oil return control method, device and multi-connected system to alleviate the above-mentioned technical problems, ensure the reliability of oil return, avoid the energy loss and usage comfort caused by excessive oil return frequency output; at the same time, it also realizes on-demand oil return and reduces the oil return frequency.

[0004] In the first aspect, an embodiment of the present invention provides an oil return control method, which is applied to a controller of a multi-split system, and the multi-split system also includes a compressor and an oil return capillary; the method includes: obtaining the outlet temperature of the oil return capillary in real time; judging whether there is refrigerant in the oil return capillary based on the outlet temperature and a preset temperature threshold; if so, performing current oil return control on the multi-split system; in the current oil return control, calculating the flow rate of the refrigerant based on calculation parameters and a preset Flooding formula; wherein the calculation parameters include: refrigerant density, oil density, gravitational acceleration, correction coefficient and the inner diameter of the pipe of the compressor suction pipe; according to the displacement and volume coefficient of the compressor, as well as the flow rate and inner diameter of the pipe, calculating the corresponding oil return frequency of the compressor in the current oil return control; controlling the compressor to operate according to the oil return frequency.

[0005] The above-mentioned oil return control method intelligently determines whether there is refrigerant in the oil return capillary according to the outlet temperature. When there is refrigerant, that is, the amount of oil inside the compressor is insufficient, the current oil return control is performed. In the oil return control, the corresponding oil return frequency of the compressor is calculated according to the calculation parameters and the preset flooding formula, thereby ensuring the reliability of oil return and avoiding energy loss and usage comfort caused by excessive oil return frequency output. At the same time, oil return is performed when the amount of oil inside the compressor is insufficient, realizing on-demand oil return, thereby reducing the oil return frequency.

[0006] Preferably, the above method also includes: obtaining the last interval duration of the multi-split system; wherein the last interval duration is used to characterize the interval duration between the multi-split system exiting the last oil return control and entering the current oil return control; judging whether the last interval duration is greater than a preset interval threshold; if so, reducing and correcting the oil return frequency according to the preset correction parameters, and controlling the compressor to operate according to the reduced and corrected oil return frequency.

[0007] Preferably, the method further comprises: if the previous interval duration is less than a preset interval threshold, increasing and correcting the oil return frequency according to a preset correction parameter, and controlling the compressor to operate according to the increased and corrected oil return frequency.

[0008] Preferably, the above method further includes: in the current oil return control, obtaining the operating time of the compressor running according to the oil return frequency, and when the operating time reaches a preset time, controlling the multi-split system to exit the current oil return control.

[0009] Preferably, the above-mentioned step of judging whether there is refrigerant in the return oil capillary based on the outlet temperature and the preset temperature threshold includes: calculating the difference between the preset temperature threshold and the outlet temperature; judging whether the difference is greater than the preset difference threshold; if so, determining that there is refrigerant in the return oil capillary.

[0010] Preferably, the above-mentioned multi-split system also includes an outdoor unit electronic expansion valve and multiple indoor unit electronic expansion valves. The method also includes: in the current oil return control, adjusting the opening of the outdoor unit electronic expansion valve to a first oil return opening, and adjusting the opening of multiple indoor unit electronic expansion valves to a second oil return opening.

[0011] Preferably, the first oil return opening is 200 pls, and the second oil return opening is 250 pls.

[0012] In a second aspect, an embodiment of the present invention further provides an oil return control device, which is applied to a controller of a multi-split system, and the multi-split system also includes a compressor and an oil return capillary; the device includes: a temperature acquisition module, which is used to obtain the outlet temperature of the oil return capillary in real time; a refrigerant judgment module, which is used to judge whether there is refrigerant in the oil return capillary based on the outlet temperature and a preset temperature threshold; an oil return control module, which is used to perform current oil return control on the multi-split system if so; a flow rate calculation module, which is used to calculate the flow rate of the refrigerant in the current oil return control based on calculation parameters and a preset Flooding formula; wherein the calculation parameters include: refrigerant density, oil density, gravitational acceleration, correction coefficient and the inner diameter of the pipe of the compressor suction pipe; a frequency calculation module, which is used to calculate the corresponding oil return frequency of the compressor in the current oil return control based on the displacement and volume coefficient of the compressor, as well as the flow rate and the inner diameter of the pipe; and an operation control module, which is used to control the compressor to operate according to the oil return frequency.

[0013] In a third aspect, an embodiment of the present invention further provides a multi-connected system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method of the first aspect when executing the computer program.

[0014] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method in the first aspect are executed.

[0015] The embodiments of the present invention bring the following beneficial effects:

[0016] The embodiments of the present invention provide an oil return control method, device and multi-split system, which intelligently judge whether there is refrigerant in the oil return capillary according to the outlet temperature. When there is refrigerant, that is, the amount of oil inside the compressor is insufficient, current oil return control is performed, and in the oil return control, the corresponding oil return frequency of the compressor is calculated according to the calculation parameters and the preset flooding formula, thereby ensuring the reliability of oil return and avoiding energy loss and usage comfort caused by excessive oil return frequency output; at the same time, oil return is performed when the amount of oil inside the compressor is insufficient, realizing on-demand oil return, thereby reducing the oil return frequency.

[0017] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description and the drawings.

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic structural diagram of a multi-connected system provided by an embodiment of the present invention;

[0021] Figure 2 A flow chart of an oil return control method provided by an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of an oil return control device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] To facilitate understanding of this embodiment, the following first introduces in detail an oil return control method provided by an embodiment of the present invention; wherein the execution subject is the controller of the multi-split system. Specifically, the multi-split system includes one outdoor unit and multiple indoor units, such as Figure 1 As shown in the figure, two indoor units are used as an example.

[0025] Among them, the outdoor unit includes a gas-liquid separator 11, a compressor 12, an oil separator 13, an outdoor heat exchanger 14 and a four-way valve 15. In addition, an exhaust temperature sensor 121 is provided in the exhaust pipe of the compressor 12, a high-pressure sensor 161 is provided on the connecting pipeline between the oil separator 13 and the four-way valve 15, and a low-pressure sensor 162 is provided on the connecting pipeline between the gas-liquid separator 11 and the four-way valve 15. The bottom of the oil separator 13 is connected to the return oil capillary 17, and an oil temperature sensor 171 is provided at the outlet of the return oil capillary 17 for detecting the outlet temperature of the return oil capillary 17; and an outdoor unit electronic expansion valve 18 is also connected to the outlet of the outdoor heat exchanger 14.

[0026] In addition, the outdoor unit is connected to multiple indoor units through air conditioning pipes and liquid conditioning pipes, such as Figure 1 As shown, a gas shutoff valve 21 is installed in the air conditioning gas pipe, a liquid shutoff valve 22 is installed on the air conditioning liquid pipe, and a filter 23 is also installed on each of the air conditioning gas pipe and the liquid pipe. Furthermore, each indoor unit also includes an indoor heat exchanger 31 and an indoor unit electronic expansion valve 32. The indoor heat exchanger 31 is also equipped with an ambient temperature sensor 33, an indoor gas pipe temperature sensor 34, and an indoor liquid pipe temperature sensor 35. It should be noted that for parts not mentioned in the multi-split system, reference can be made to existing multi-split systems for details, and the embodiments of the present invention will not be described in detail here.

[0027] Based on the above multi-connected system, an embodiment of the present invention provides an oil return control method, such as Figure 2 As shown, the method includes the following steps:

[0028] Step S202, obtaining the outlet temperature of the oil return capillary in real time;

[0029] Specifically, for a multi-split system, when there is oil in the oil separator 13, refrigeration oil circulates in the return oil capillary 17; when there is no oil in the oil separator 13, high-pressure gaseous refrigerant, i.e., refrigerant, circulates in the return oil capillary 17; due to the huge difference in specific heat capacity and density between refrigeration oil and gaseous refrigerant, according to the heat transfer formula, when refrigeration oil or gaseous refrigerant flows through the return oil capillary 17, due to the different heat dissipation, the outlet temperature of the return oil capillary 17 will be greatly different.

[0030] In practical applications, the specific heat capacity of oil c can be obtained from the physical properties of the medium: v油 =1870J / (kg,℃), density is ρ 油 =852kg / m 3 Specific heat capacity of refrigerant c v冷媒 =1131J / (kg,℃), density is ρ 冷媒 =40.45kg / m 3 ;The heat transfer formula is shown as follows:

[0031] Q=(t0-t)hA=(t1-t2)c v ρV (1)

[0032] Where Q represents heat, h represents the total heat transfer coefficient, t0-t and t1-t2 represent temperature changes, A represents the heat exchange area, c v represents specific heat capacity, ρ represents density, and V represents the volume of fluid in the oil return capillary.

[0033] Based on the above formula (1), when the refrigeration oil and the refrigerant pass through the oil return capillary 17 respectively, the difference in heat transfer is times, and the difference in heat transfer leads to a difference in the outlet temperature of the oil return capillary 17.

[0034] Therefore, an oil temperature sensor 171 is provided at the outlet of the return oil capillary 17 to detect the outlet temperature of the return oil capillary, so that the controller can accurately judge whether there is oil in the oil separator 13 according to the difference in the change of the outlet temperature of the return oil capillary. When there is no oil in the oil separator 13, it can be inferred that there is also no oil in the compressor 12, so that the outlet temperature of the return oil capillary can be used as the basis for judging the oil amount in the compressor.

[0035] It should be noted that the outlet temperature of the above-mentioned return oil capillary can be obtained according to a preset cycle or in real time. In order to facilitate timely return oil control, the controller in the embodiment of the present invention obtains the outlet temperature of the return oil capillary collected by the oil temperature sensing package 171 in real time.

[0036] Step S204: determining whether there is refrigerant in the oil return capillary according to the outlet temperature and a preset temperature threshold;

[0037] Specifically, for the real-time detected outlet temperature T of the oil return capillary oil , calculate the preset temperature threshold T out and outlet temperature T oil The difference between them; determine whether the difference is greater than the preset difference threshold a; if so, determine that there is refrigerant in the return oil capillary; that is, when T out -T oil When the difference is greater than a, it indicates that the oil return capillary is not entirely filled with oil and refrigerant is present, indicating that the compressor is at risk of oil shortage. At this time, the multi-split system enters oil return control. The preset difference threshold a ranges from 5 to 10, preferably 8.

[0038] For the above preset temperature threshold T out It can be determined based on the outlet temperature of the oil return capillary when the compressor oil volume is sufficient. Since the oil is discharged with the compressor, the temperature T in the oil separator in = compression exhaust temperature - oil dispersion heat loss k, so the outlet temperature of the oil return capillary at this time is the preset temperature threshold T out =T in - Heat dissipation loss of the oil return capillary tube h; wherein, the value range of k is 3-7, preferably 5; the value range of h is 5-10, preferably 8. It should be noted that due to the differences in the optional size of the oil separator and the length of the oil return capillary tube, k and h can be set according to actual conditions.

[0039] Step S206: If yes, perform current oil return control on the multi-split system;

[0040] Specifically, the refrigerant oil inside the compressor 12 enters the oil separator 13 along with the exhaust gas, and most of the oil returns to the compressor 12 through the oil return capillary 17; however, the oil separation efficiency of the oil separator 13 varies, and a small amount of oil will circulate throughout the refrigeration system with the refrigerant and adhere to the inner wall of the copper tube. If the oil is not returned for a long time, more and more oil will be discharged, resulting in oil shortage in the compressor 12.

[0041] Therefore, when it is determined that there is refrigerant in the oil return capillary based on the outlet temperature and the preset temperature threshold, the compressor oil volume is insufficient and oil return action is required, that is, the controller performs oil return control on the multi-split system. For the sake of convenience, the oil return control at this time is referred to as the current oil return control.

[0042] Step S208: In the current oil return control, the flow rate of the refrigerant is calculated according to the calculation parameters and the preset flooding formula;

[0043] Specifically, the calculation parameters include: refrigerant density, oil density, gravity acceleration, correction coefficient, and the inner diameter of the compressor suction pipe; these calculation parameters can be pre-stored in the controller to improve the efficiency of refrigerant flow rate calculation. Among them, the conventional flooding formula is as follows:

[0044] F=ρ gas 1 / 2 ×V gas / ((ρ oil -ρ gas )×g×d) 1 / 2 (2)

[0045] Among them, ρ gas Indicates the refrigerant density, V gas Represents the flow rate of the refrigerant, ρ oil represents the oil density, g represents the acceleration due to gravity, and d represents the inner diameter of the pipe.

[0046] According to the above flooding formula, in order to overcome the gravity of the refrigeration oil, it is necessary to require flooding ≥ 1.2. Here, let flooding = 1.2, that is, F = 1.2. The refrigerant flow rate can be calculated according to the following formula:

[0047] V gas =F×((ρ oil -ρ gas )×g×d) 1 / 2 / ρ gas 1 / 2 ×S (3)

[0048] Among them, ρ gas Indicates the refrigerant density, V gas Represents the flow rate of the refrigerant, ρ oil represents the oil density, g represents the acceleration due to gravity, d represents the inner diameter of the pipe, and S represents the correction coefficient. It should be noted that in the oil return control, the correction coefficient S is preferably 2.

[0049] Step S210, calculating the oil return frequency corresponding to the compressor in the current oil return control according to the displacement and volume coefficient of the compressor, as well as the flow rate and the inner diameter of the pipe;

[0050] In practice, the typical oil return method is to increase the compressor frequency to increase the refrigerant flow rate and remove the refrigerant oil adhering to the copper pipes. However, at the same frequency, different refrigerant parameters (such as high pressure, low pressure, and superheat) will result in different refrigerant flow rates. If the frequency is set too high, the comfort will be greatly affected, while if the frequency is set too low, the oil return effect will be affected. Therefore, accurately calculating the compressor's oil return frequency is of great significance.

[0051] Specifically, the oil return frequency is calculated according to the following formula:

[0052]

[0053] Among them, f oil Indicates the oil return frequency, V gas Indicates the flow rate of the refrigerant, d indicates the inner diameter of the pipe, V cc represents the displacement of the compressor, η represents the volume coefficient of the compressor, and its value range is 0.92~0.98, preferably 0.95.

[0054] Therefore, after calculating the refrigerant flow rate in real time using the calculation parameters and the preset flooding formula, the oil return frequency required by the compressor is calculated according to the above formula (4), ensuring the reliability of the oil return and avoiding energy loss and usage comfort caused by excessive oil return frequency output.

[0055] Step S212: Control the compressor to operate according to the oil return frequency.

[0056] Specifically, in the current oil return control, the controller controls the compressor according to the oil return frequency f oil Operation, that is, controlling the compressor to adjust from the current operating frequency to the oil return frequency f oil In addition, in the current oil return control, the controller also obtains the compressor according to the oil return frequency f oil The running time of the operation is set, and when the running time reaches the preset time N, the multi-connected system is controlled to exit the current oil return control. Here, the value range of N is 3 minutes to 5 minutes, preferably 3 minutes.

[0057] Preferably, the method further comprises: in the current oil return control, adjusting the opening of the outdoor unit electronic expansion valve to the first oil return opening, and adjusting the opening of the electronic expansion valves of the plurality of indoor units to the second oil return opening. Specifically, the controller controls the compressor according to the oil return frequency f oil During operation, the opening of the outdoor unit's electronic expansion valve is also adjusted from its current opening to the first oil return opening. This first oil return opening is conventional oil return control, meaning it remains fully open during cooling and is adjusted to the first oil return opening during heating. The first oil return opening has a value range of 160 pls to 300 pls, preferably 200 pls. Simultaneously, the openings of multiple indoor unit electronic expansion valves are adjusted from their current openings to the second oil return opening. This second oil return opening is a fixed value, ranging from 200 pls to 300 pls, preferably 250 pls. This further ensures the oil return efficiency and reliability of the VRF system by adjusting the compressor's oil return frequency and the openings of the outdoor and indoor electronic expansion valves.

[0058] The oil return control method provided by the embodiment of the present invention intelligently determines whether there is refrigerant in the oil return capillary according to the outlet temperature. When there is refrigerant, that is, the amount of oil inside the compressor is insufficient, current oil return control is performed. In the oil return control, since different calculation parameters lead to different refrigerant flow rates, the refrigerant flow rate is calculated in real time according to the calculation parameters and the preset Flooding formula to calculate the corresponding oil return frequency of the compressor, thereby ensuring the reliability of oil return and avoiding energy loss and usage comfort caused by excessive oil return frequency output; at the same time, oil return is performed when the amount of oil inside the compressor is insufficient, realizing on-demand oil return, thereby reducing the oil return frequency.

[0059] Furthermore, the above method also includes: obtaining the last interval duration ta(n-1) of the multi-connected system; wherein, the last interval duration ta(n-1) is used to characterize the interval duration between the multi-connected system exiting the last oil return control and entering the current oil return control; judging whether the last interval duration ta(n-1) is greater than the preset interval threshold t; if so, reducing and correcting the oil return frequency according to the preset correction parameter, and controlling the compressor to operate according to the reduced and corrected oil return frequency. Specifically, when ta(n-1)>t, reducing and correcting the oil return frequency according to the preset correction parameter (preferably 5%), that is, in the current oil return control, calculating the oil return frequency f oil Then, on this basis, the oil return frequency f is reduced by 5% according to the frequency change. oil Perform frequency correction and use the oil return frequency after reduction correction as the final oil return frequency of the compressor.

[0060] In addition, if the previous interval duration ta(n-1) is less than the preset interval threshold t, the oil return frequency is increased and corrected according to the preset correction parameter, and the compressor is controlled to operate according to the increased and corrected oil return frequency. That is, when ta(n-1) < t, the oil return frequency is increased and corrected according to the preset correction parameter, that is, in the current oil return control, the oil return frequency f is calculated. oil Then, on this basis, the oil return frequency f is increased by 5% according to the frequency change. oil The frequency correction is performed, and the increased oil return frequency after correction is used as the final oil return frequency of the compressor. The preset interval threshold value t has a value range of 3 hours to 5 hours, preferably 4 hours.

[0061] Therefore, when the oil return volume is insufficient, the compressor will enter the oil return phase again after a short period of operation. That is, when the interval between two oil return controls is too short, it indicates that the currently calculated oil return frequency is too low and the oil return effect is poor. When entering the oil return control next time, the controller will automatically correct the calculated oil return frequency to increase the oil return volume.

[0062] In summary, the oil return control method provided by the embodiment of the present invention intelligently judges the oil amount inside the compressor based on the outlet temperature in the oil return capillary, achieves oil return on demand, reduces the frequency of oil return, and avoids energy loss and usage comfort caused by frequent oil return; in addition, during the oil return process, the flow rate of the refrigerant is calculated in real time according to the calculation parameters and the preset Flooding formula, so as to calculate the corresponding oil return frequency of the compressor, thereby realizing precise control of the oil return effect, thereby ensuring the reliability of the oil return, and avoiding energy loss and usage comfort caused by excessive oil return frequency output; and, combined with the oil return interval, that is, the preset interval threshold t, the oil return frequency of the compressor in the next oil return control is automatically corrected, further ensuring the oil return effect of the multi-split system.

[0063] Corresponding to the above method embodiment, the embodiment of the present invention further provides an oil return control device, which is applied to a controller of a multi-split system, wherein the multi-split system further includes a compressor and an oil return capillary. Figure 3 As shown, the device includes: a temperature acquisition module 31, a refrigerant judgment module 32, an oil return control module 33, a flow rate calculation module 34, a frequency calculation module 35 and an operation control module 36; wherein, the functions of each module are as follows:

[0064] The temperature acquisition module 31 is used to obtain the outlet temperature of the oil return capillary in real time;

[0065] A refrigerant determination module 32 is configured to determine whether there is refrigerant in the oil return capillary according to the outlet temperature and a preset temperature threshold;

[0066] The oil return control module 33 is used to perform current oil return control on the multi-split system if yes;

[0067] The flow rate calculation module 34 is used to calculate the flow rate of the refrigerant according to the calculation parameters and the preset flooding formula during the current oil return control. The calculation parameters include: refrigerant density, oil density, gravity acceleration, correction coefficient, and the inner diameter of the compressor suction pipe;

[0068] The frequency calculation module 35 is used to calculate the oil return frequency corresponding to the current oil return control of the compressor based on the displacement and volume coefficient of the compressor, as well as the flow rate and the inner diameter of the pipe;

[0069] The operation control module 36 is used to control the compressor to operate according to the oil return frequency.

[0070] The oil return control device provided in an embodiment of the present invention intelligently determines whether there is refrigerant in the oil return capillary according to the outlet temperature. When there is refrigerant, that is, the amount of oil inside the compressor is insufficient, current oil return control is performed, and in the oil return control, the oil return frequency corresponding to the compressor is calculated according to the calculation parameters and the preset Flooding formula, thereby ensuring the reliability of oil return and avoiding energy loss and usage comfort caused by excessive oil return frequency output; at the same time, oil return is also performed when the amount of oil inside the compressor is insufficient, realizing on-demand oil return, thereby reducing the oil return frequency.

[0071] Preferably, the above-mentioned device also includes: obtaining the last interval duration of the multi-split system; wherein the last interval duration is used to characterize the interval duration between the multi-split system exiting the last oil return control and entering the current oil return control; judging whether the last interval duration is greater than a preset interval threshold; if so, reducing and correcting the oil return frequency according to the preset correction parameters, and controlling the compressor to operate according to the reduced and corrected oil return frequency.

[0072] Preferably, the above device further comprises: if the previous interval duration is less than a preset interval threshold, increasing and correcting the oil return frequency according to a preset correction parameter, and controlling the compressor to operate according to the increased and corrected oil return frequency.

[0073] Preferably, the above device further includes: in the current oil return control, obtaining the operating time of the compressor running according to the oil return frequency, and when the operating time reaches a preset time, controlling the multi-connected system to exit the current oil return control.

[0074] Preferably, the refrigerant determination module 32 is further configured to: calculate the difference between a preset temperature threshold and the outlet temperature; determine whether the difference is greater than the preset difference threshold; and if so, determine that refrigerant exists in the oil return capillary.

[0075] Preferably, the above-mentioned multi-split system also includes an outdoor unit electronic expansion valve and multiple indoor unit electronic expansion valves. The device also includes: in the current oil return control, adjusting the opening of the outdoor unit electronic expansion valve to the first oil return opening, and adjusting the opening of the multiple indoor unit electronic expansion valves to the second oil return opening.

[0076] Preferably, the first oil return opening is 200 pls, and the second oil return opening is 250 pls.

[0077] The oil return control device provided in the embodiment of the present invention has the same technical features as the oil return control method provided in the above embodiment, and therefore can also solve the same technical problems and achieve the same technical effects.

[0078] An embodiment of the present invention further provides a multi-connected system, including a processor and a memory, wherein the memory stores machine executable instructions that can be executed by the processor, and the processor executes the machine executable instructions to implement the above-mentioned oil return control method.

[0079] This embodiment further provides a machine-readable storage medium storing machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the above-mentioned oil return control method.

[0080] The oil return control method, device, and computer program product of the multi-split system provided in the embodiments of the present invention include a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the previous method embodiments. For specific implementation, please refer to the method embodiments and will not be repeated here.

[0081] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems and devices can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0082] In addition, in the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0083] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0084] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0085] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. An oil return control method, characterized in that: A controller applied to a multi-split system, wherein the multi-split system further includes a compressor and an oil return capillary; the method includes: obtaining the outlet temperature of the oil return capillary in real time; determining whether there is refrigerant in the oil return capillary according to the outlet temperature and a preset temperature threshold; If yes, performing current oil return control on the multi-connected system; In the current oil return control, the flow rate of the refrigerant is calculated based on calculation parameters and a preset flooding formula; wherein the calculation parameters include: refrigerant density, oil density, gravity acceleration, correction coefficient, and the inner diameter of the compressor suction pipe; Calculating the oil return frequency of the compressor in the current oil return control according to the displacement and volume coefficient of the compressor, the flow rate, and the inner diameter of the pipe; controlling the compressor to operate according to the oil return frequency; The expression of the preset Flooding formula is as follows: V gas =F×((ρ oil -r gas )×g×d) 12 / r gas 12 ×S Among them, V gas represents the flow rate of the refrigerant, ρ gas represents the refrigerant density, ρ oil represents the oil density, g represents the gravitational acceleration, S represents the correction coefficient, d represents the pipe inner diameter, and F=1.

2.

2. The method according to claim 1, characterized in that The method further comprises: Obtaining the last interval duration of the multi-connected system; wherein the last interval duration is used to represent the interval duration between the multi-connected system exiting the last oil return control and entering the current oil return control; Determine whether the previous interval duration is greater than a preset interval threshold; If so, the oil return frequency is corrected to decrease according to a preset correction parameter, and the compressor is controlled to operate according to the oil return frequency after the correction.

3. The method according to claim 2, characterized in that The method further comprises: If the previous interval duration is less than the preset interval threshold, the oil return frequency is increased and corrected according to the preset correction parameter, and the compressor is controlled to operate according to the increased and corrected oil return frequency.

4. The method according to any one of claims 1 to 3, characterized in that The method further comprises: In the current oil return control, the operating time of the compressor running at the oil return frequency is obtained, and when the operating time reaches a preset time, the multi-connected system is controlled to exit the current oil return control.

5. The method according to claim 1, wherein The step of determining whether there is refrigerant in the oil return capillary according to the outlet temperature and a preset temperature threshold comprises: calculating a difference between the preset temperature threshold and the outlet temperature; Determining whether the difference is greater than a preset difference threshold; If yes, it is determined that the refrigerant exists in the oil return capillary.

6. The method according to claim 1, characterized in that The multi-split system further includes an outdoor unit electronic expansion valve and a plurality of indoor unit electronic expansion valves, and the method further includes: In the current oil return control, the opening degree of the outdoor unit electronic expansion valve is adjusted to a first oil return opening degree, and the opening degrees of the plurality of indoor unit electronic expansion valves are adjusted to a second oil return opening degree.

7. The method according to claim 6, characterized in that The first oil return opening is 200 pls, and the second oil return opening is 250 pls.

8. An oil return control device, characterized in that: A controller for a multi-split system, wherein the multi-split system further includes a compressor and an oil return capillary; the device includes: A temperature acquisition module, used for acquiring the outlet temperature of the oil return capillary in real time; a refrigerant determination module, configured to determine whether refrigerant is present in the oil return capillary according to the outlet temperature and a preset temperature threshold; an oil return control module, configured to, if yes, perform current oil return control on the multi-split system; a flow rate calculation module, configured to calculate the flow rate of the refrigerant in the current oil return control according to calculation parameters and a preset flooding formula; wherein the calculation parameters include: refrigerant density, oil density, gravity acceleration, correction coefficient, and inner diameter of the compressor suction pipe; a frequency calculation module, configured to calculate the oil return frequency of the compressor in the current oil return control according to the displacement and volume coefficient of the compressor, the flow rate, and the inner diameter of the pipe; An operation control module, configured to control the compressor to operate according to the oil return frequency; The expression of the preset Flooding formula is as follows: V gas =F×((ρ oil -r gas )×g×d) 12 / r gas 12 ×S Among them, V gas represents the flow rate of the refrigerant, ρ gas represents the refrigerant density, ρ oil represents the oil density, g represents the gravitational acceleration, S represents the correction coefficient, d represents the pipe inner diameter, and F=1.

2.

9. A multi-connection system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are executed.

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